Gelatin preparation



p i 8, 1944. w. M. URBAIN 2,346,880

GELATIN PREPARATION Filed May 2, 1941 A TORNEY Patented Apr. 18, 1944GELATIN PREPARATION Walter M. Urbain, Chicago, 111-, assignor toIndustrial Patents Corporation, Chicago, 111., a corporation of DelawareApplication May 2, 1941, Serial No. 391,461

16 Claims.

This invention relates to the preparation of dry protein material in asubstantial sterile condition, and more particularly it is directed to amethod and apparatus for preparing gelatin suitable for edible purposessubstantially free from bacteria and molds.

Gelatin is commonly prepared by a method. involving hot aqueousextraction from a suitable source material such as hides or bones whichhave had albuminous and mucinous matter removed therefrom, concentrationof the aqueous gelatin extract in evaporators, spreading of theconcentrated gelatin solution as a thin film upon a moving belt,chilling the concentrated gelatin on the belt until it sets up into ajelly, removing the wet gelatin film from the moving belt, and drying iton a suitable support. As is clearly evident, the product, especiallywhen employed in food preparations, should be substantially free ofbacteria. Every precaution is therefore employed by the manufacturers toprevent containination of the gelatin product with bacteria or mold.However, it has been found that even when operating under very closelycontrolled, sanitary conditions throughout the process, the finalproduct will often be infected with bacteria. This unfortunate resultseems to occur more frequently in the summer than in the winter. Adetailed study has shown that the chilled gelatin jelly is generallyfree from bacteria but that the dried film is usually contaminated.

It has now been found that the source of contamination is the presenceof bacteria on the supports for the chilled gelatin film during thedrying period. Even though these supporting frames or screens are keptin a clean condition it has been found that they are the origin of thecontamination. If the frames are free of bacteria there seems to be nosubstantial development of bacteria in the gelatin film during the hotdrying period. The drying step is particularly conducive to bacteriadevelopment because of the increased temperature for substantial periodsof time, but it has been found that in normal operation unless thegelatin is infected by the frames or supports during this period thereis no substantial increase in bacteria count. However, the screens whichare re-used for supporting fresh sheets to be dried are found to developbacteria rather readily.

In spite of the fact that attempts are made to keep the frames clean,they retain small particles of gelatin which, because of the nature ofthe frame or screen surfaces, are not always removed in the cleaningprocess. The gelatin particles, lumps or films serve as fuel ofinfection for subsequent sheets of jelly. Because of the longer periodthat these contaminated particles of gelatin are in the Warm air dryingchamber they develop an exceptionally high bacteria count. Theseinfected areas in contact with the gelatin sheet undergoing dryinginfect the sheet. The drying period then amounts to an incubation whichdevelops the infection, resulting in a high count gelatin. In thesummertime the usual high humidity necessarily increases the drying timeand consequently increases the incubation period.

Wet methods of cleaning and sterilizing the upporting screens are notdesirable because the wood framework of the screens onrepeated wettingand drying will harden and sometimes twist out of shape. Furthermore,the process is long, and the labor costs are very high. Dry methods ofdisinfecting the screens likewise cause'drying out and breaking of Woodframes, and as in the wet method take considerable time. Chemicalmethods have the added-disadvantage of the possibility of contaminationof the edible gelatin to be dried while supported on t e frames. Becauseof the infection througliout the gelatin particles or filmscontaminating the screen, simple surface-sterilizing methods cannot beused alone.

It has now been found possible to prepare gelatin substantially freefrom bacteria conveniently by the standard procedures. The presentprocess comprises, in general, the irradiation of the supporting frameswith ultra-violet radiation of sufilcient intensity to materiallydisinfect the frames including the gelatin contaminant thereon justprior to placing on said frame the gelatin jelly sheet to be dried inthe air drying chamber. Until this invention, it has been generallyaccepted that ultra-violet radiation could only be used for air andsurface sterilization or for sterilization of thin films of water or thefew other substances which similarly readily transmit ultraviolet light.On the contrary, it has now been determined that it is possible tosterilize substantia1 thicknesses of gelatin particles infected withbacteria not only at the surface but substantially throughout it in avery short time of exposure and at a relatively low cost. Consideringthe relatively great thickness of the gelatin films orparticle's which.adhere to the screens or frames git is'surprising that thesubstantialsterilization-of the frames and adherent gelatin particlescanbe effected by the present process sincethe absorption ofultra-Violet rays is yery great by even thin layers of material andincreases rapidly with inthat the ultra-violet light from a 3.5 amperemercury vapor lamp at a distance of centimeters had only a superficialactionon gelatin gel and that it did not proceed deeper after a certainminimum duration of exposure because of the opacity of gelatin to raysof short wave length.

In addition, Steenbock, United States Patent No.

1,871,135, discloses that with the ordinary mercury vapor lampirradiation of various materials, among which is gelatin, antirachiticactivation is effected but not sterilization. However, substan tiallycomplete sterilization has been effected in a' fraction of a minute bythe present method. This is startling since sterilization of otherorganic compounds by earlier ultra-violet procedures either wasefi'ected in very thin films, or wasaccomplished with thickerparticlesjsu'ch as lumpy sugar which could not be sterilized in fiftyminutes by direct radiation, only after two minutes of treatment byshakingto expose fresh surfaces.

(J, Ind. and Eng. Chem, vol. 31, p. 1168, 1939.)

It has been discovered that it is essential that the effectiveultra-violet radiation be of suflicient intensity that the rayspenetrating through substantial layers of material are still ofsufficient intensity, e. g., about microwatts per square millimeter, tocause a rapid abiatic action. This is obtained by a highintensity sourceof ultraviolet radiation in excess of 25 microwatts per squaremillimeter (at the surface) by an amount governed by the thickness andthe coflicient of absorption of the gelatin or other protein contaminanton the creen. For example, with average conditions of operation thesurface intensity of 50 to 100 microwatts per square millimeter ofactive radiation has been found satisfactory although less may proveoperative depending on the type and intensity of contamination and timeof treatment. The period of treatment preferably should be sufficientlylong to yield substantial tancy for radiation of wave lengths shorterthan 2,800 Angstroms. Therefore, believing that sterilization could notbe eifected, earlier workers erations. Some of the inoculated gelatincoated screens were irradiated with a three hundred and sixty wattUviarc lamp at a distance of about eight inches for differentirradiation periods. Following the irradiation a sterile 10% aqueousgelatin jelly was laid on the screens and after incubation at roomtemperature for 24 hours this gelatin was dried in a wind tunnel andstripped oflthe screens aseptically. The bacterial count of this gelatinfrom the different frames was observed and the results are given in thefollowing Prior either would not have attempted to sterilize the gelatinby this means or would have used the usuallow intensity ultra violetsources to accomplish the result of'questionable value; namely, simplesurface'sterilization.

The ability of high intensity radiation to penetrate gelatin isdemonstrated by the following experiment. A number of gelatin dryingscreens employed in conjunction witha K. & L. gelatin casting machinewere dipped in a10% aqueous gelatin solution which had a high'bacteriacount. The gelatin adhering to the screens was permitted to dry. To thecoated screens was then applied a gelatin jelly prepared from the highcount solution, after which the screens were. again dried. These piecesof 'jelly were about one-fourth inch thick and oneinchin' diameterbeforedrying, and shrank toa thickness of about one-sixteenth inch afterdrying; Particles. this ..size are about as w seny a eeted;.e qlieerriet rl n- It is apparent from these results that the dried gelatin fromthe highly contaminated screens which had been irradiated by the highintensity ultra-violet rays had a much lower and more satisfactorybacterial count. The conclusion is therefore drawn that the radiationfrom the high intensity Uviarc lamp was of suflicient intensity that inthe short time periods listed sufficient penetration was obtained tosubstantially sterilize the contaminated gelatin present in relativelythick pieces. The 360 watt fused quartz mercury arc lamp or Uviarc lampemployed in the above experiment has an arc length of about six inchesmaximum, a rating of 54 watts per arc inch, and develops 284 microwattsof ultra-violet energy per square millimeter at 10 centimeters. It hasan over-all length of 10 inches and a diameter of inch maximum. Theradiation characteristics of the lamp are as follows:

This data indicates that the lamp is ahigh intensity lamp and is not tobe confused with the low intensity germicidal or Sterilamps commonlyemployed for surface sterilization.

Although good results are obtained by using the lamps alone, it has beenfound advantageous to employ reflectors for the lamps notonly in back ofthe lamps but on the other side of'the screens in order to throw back asmuch of the ultra-violet light as possible, thus increasing theefficiencies of the lamps about 50%, and alsopro- -te cting the workersin the surrounding; area.

The metal employed affects the efiiciency of reflection, the order ofpreference being roughly: stainless steel, stellite, nickel plate,polished aluminum, polished tin and Duralumin. i

In commercial operation the location for the installation of theultra-violet lamps depends on the'following considerations: I

1. The lamps must effectively irradiate all the surfaces of the screens.

2. Sufiicient exposure must be obtained by the correct combination. ofthe number of lamps, intensity of radiation, and time of exposure.

3.- The interval of time between irradiation and use of thescreensshould be as short as possible.

4. The lamp should be mounted so as not to interfere with the continuousoperation of the chilling and drying apparatus, e. g., a K. 8: L.machine.

5. Protection must be provided for the operators against the actinicrays and glare, and ozone generated by the lamp. r

The commercial installation represented in Figures I and II of theaccompanying drawing represents a satisfactory compliance with the abovelisted requirements in a & L. apparatus.

Figure I is a side elevation of a modified K. 8: L.

I passes over the large drum 3 the gelatin jelly u sheet is strippedfrom the belt I by scraper 5. The gelatin jelly sheet 4 is then carriedby the endless take-oif belt 6 on a series of pulleys to the rotarycutter l which cuts the jelly sheet into two longitudinal strips. Thegelatin strips are then cut transversely by rotary cutter 8 into sheetsabout five feet long. The high intensity lamps 9 are mounted below theendless belt 6. Mounting them in this position requires the raising ofthe take-off belt 6 from its usual position to make room for the lampswhich are in the enclosing hood IZ. In the large scale apparatus forcommercial production employing 1,200 watt lamps, it is usuallydesirable to place two or three pairs of lamps side by side so that theradiation coversabout three feet of the length and the entire width ofthe frames or screens I0, moving on the endless open belt or chain I Iat a distance of about eight inches under the lamps 9. This develops atleast 300 microwatts per square millimeter of active ultra-violetradiation. Four such lamps are generally sufficient to provideadequateexposure when the K & L. chilling belt I is operated at maximumspeed, usually about ten feet per minute. A polished stainless steelreflection plate I3 is placed under the screen to reflect a substantialquantity of the ultraviolet light and to increase the efiiciency of thelamps. The screens I0, substantially sterilized by the treatment at thispoint, move but a short distance before the cut chilled gelatin strips 4are placed thereon by the take-off belt 6; hence no appreciable timeintervenes between the sterilization and use of the screens. The loadedscreens are removed from the endless belt as it passes over the gear I4and are placed on movable supporting racks (not shown) which are removedto a drying chamber through which passes a stream of warm, relativelydry air. Protection for the workers against actinic rays and glare isprovided by the hood l2 and suitable shielding. Ozone generated by thelamps is removed by drawing air by means of an exhaust fan (not shownlout of the room past the lamps 9 at a rate of- 2,000 cubic feet a minutethrough the twelve inch duct l5. "Ihis ventilation also serves to coolthe lamps 9, adding to their effective life. The following table showsthe effectiveness of the radiation of the screens in commercialproduction of gelatin satisfactory from a bacterial standpoint.

TABLE III Conveyor Irradiation period per Bacteria of lamps g g fi unitarea. per gm.

' sec.

6 16 '30 0 l6 40 6 l6 l0 6 0 10,000, 000 6 0 4, 300,000 6 o 11, 000, 000

I0 10 120 10 10 70 l0 i0 10 0 300, 000 10 0 300. 000 10 0 780, 000

In obtaining the above data artificial drying conditions approximatinghigh humidity or delayed drying operation were made by holding theterlstics:

TABLE IV Electrical data Arc watts 1200 Arc length -inches 12.5 Insidediameter do 0.7 Volts 350 Amperes 4 Radiation characteristics MicrowattsWavelength,

per sq. cm. Angstroms at 1 meter It develops about 1,420 microwatts persquare millimeter of active ultra-violet radiation at ten centimeters.The above characteristics including power consumption and ultra-violetradiation output demonstrate that this is a high intensity source ofultra-violet. This lamp may be effectively employed at distances of twofeet from the irradiated surface.

A satisfactory lam-p should have sufiicient radiation of low wavelengthbelow the limit of about 3,600 Angstrorns. The shortest rays have themost lethal action and .it is preferred to employ lamps emanating asubstantial radiation having. wavelengths less than 2,800 Angstroms; The1,200 watt lamps not only has 17% of its radiation in th highly activerange, but its high overall .powerproduce an exceptionally high quantityof total short wave radiation. In other words, there is a great quantityof high intensity radiation that is well above the minimum thresholdintensity of ultra-violet radiation to effect lethal action, usually ofthe order of 25 microwatts per square millimeter. Above this value thelethal action depends on the time and to a great extent on the intensityof ultra-violet radiation, which two values fix the total quantity ofradiation. Although about 5,000 microwatt seconds per squaremillimeterradiation is extremely effective with the above-discussed lamp underordinary conditions of operation,increased intensity of activeultra-violet radiation may reduce this volume, and vice versa. Theintensityof .the 1,200 watt lamp is so exceptionally high that not onlyshort times of exposure are possible, but even in those short times morethan simple surface sterilization is obtained.

The present operation is so eifec'tive'that, even though periodicwashingof the screens is given for assuring proper operation,the screensare sterilized without the removal of' the substantial quantities ofaccumulated gelatin on the screens usually accomplished by suchwashings.

The ordinary germicidal or sterilamps have an operating wattage of onlyabout ten' to fifteen watts, or about one to one and one-half watts perarc inch, and a highly active ultra-violet intensity of only fifteen to.twenty microwatts per square millimeter at ten centimeters. The 1,200watt lamp develops about seventy to ninetyfive times the ultra-violetlight produced by the usually employed lamp. To accomplish the sameresult with the small commercial low-intensity lamps as with the largehigh-intensity lamp is not only impractical, but probably impossiblebecause of the problem of getting sufiicient lamps in a position toirradiate simultaneously the same surface with about the same energyconsumption.

The above procedure for treating the screens is substantially dilferentthan the direct irradiation of dry gelatin, gelatin solutions or gelatinjelly, since it elfects the production of substantially sterile gelatinwithout physical modification or deterioration which results fromtreating gelatin directly with ultra-violet radiation. Treatment ofgelatin in various forms with certain ultra-violetradiation will affectthe viscosity, solubility, swelling, whipping properties, taste, odorand various other properties, depending on the form during treatment aswell as the duration and intensity of treatment.

As many widely different modifications and embodiments of the inventionhereinbefore set forth may be made without departing from the spirit andscope thereof, only such limitations should be imposed as are indicatedin the following claims.

I claim: I

,1. In the process of drying films of gelatin jelly, the. steps whichcomprise irradiating the drying frame with high intensity ultra-violetradiation of an intensity greater than twenty-five microwatts per squaremillimeter for a time suflicient to substantially sterilize the framesand any gelatin adhering thereto and prior to any substantialrecontamination applying a gelatin film for drying on the sterilizedframe so that a sub stantially sterile film'o'f gelatin jelly driedthereon is 'obtained;-

1 '2. In the process of drying films of gelatin jelly, the steps whichcomprise irradiating the drying support with ultra-violet radiation ofan plying gelatin to the sterilized support for drying.

3. In the process of drying films of gelatin jelly, the step whichcomprises irradiating the drying support immediately prior to placingthe gelatine to be dried thereon with the rays from at least one twelvehundred watt, high intensity, ultra-violet, fused quartz, mercury arclamp at a distance of not more than two feet from the frame for a periodsufficient to sterilize the support and any gelatin adhering thereto.

4. In the process of drying films of gelatin jelly, the steps whichcomprise irradiating the drying support with ultra-violet radiation ofan intensity of not less than fifty microwatts per square millimeter fora sufficient period to substantially sterilize the support and anygelatin adhering thereto and promptly thereafter applying to thesterilized support the gelatin for drying.

5. In the proces of drying films of gelatin jelly, the step whichcomprises irradiating the drying support immediately prior to placingthe gelatin to be dried thereon with ultra-violet radiation of anintensity of not less than fifty microwatts per square millimeter for asufiicient period that the total irradiation is five thousand microwattseconds per square millimeter.

6. In the process of drying films of gelatin jelly, the step whichcomprise irradiating the drying support with ultra-violet radiation ofan intensity of not less than one hundred microwatt per squaremillimeter for a sufiicient period to substantially sterilize thesupport and any gelatin adhering thereto and prior to any substantialrecontamination applying gelatin to the sterilized support for drying.

7. In the process of drying films of gelatin jelly, the step whichcomprise irradiating the drying support with ultra-violet radiation ofan intensity of not less than three hundred micro- Watts per squaremillimeter for a sufficient period to substantially sterilize thesupport and any gelatin adhering thereto and promptly thereafterapplying to the sterilized support the gelatin for drying.

8. In the process of drying films of gelatin jelly, the step whichcomprises irradiating ,the drying support with ultra-violet radiation ofan intensity of not less than three hundred microwatts per squaremillimeter for a period of time that the total irradiation i fivethousand microwatt seconds per square millimeter, said irradiation beingmade just prior to the placing of the gelatin jelly film thereon. 1

9. A process for the manufacture of dried gelatin material of lowbacterial content wherein gelatinous material is dried on a dryingsupport normally tending to retain impurities which contaminate thegelatin dried thereon, which comprises treating the support withultraviolet radiation of sufiicient high intensity to substantiallysterilize the surface of the support and any particles of gelatinmaterial retained thereon and immediately thereafter placing thegelatinous material on said support for drying.

' 10. A process for the manufacture of edible gelatin of low bacterialcount wherein the gelatin jelly is dried in films on screens normallytending to retain on the surface thereof impurities, including particlesof gelatin which contain a high bacterial count, and to contaminate thegelatin films dried thereon, which comprises subjecting the screens toultra-violet radiation of suiiicient high intensity to substantiallysterilize the surface thereof and any particles of gelatin adheringthereto and immediately drying the gelatin films on the sterilizedscreens.

11. In an apparatus for treating gelatin, the combination of a source ofultra-violet radiation, a reflector, means for conveying gelatin screensbetween the source of radiation and the reflector, and means fordepositing films of gelatin on the screens immediately after passingbetween said source of radiation and said reflector.

12. In an apparatus for treating gelatin, the combination of a conveyormeans for gelatin screens, a second conveyor means superimposed on saidfirst conveyor means for depositing sheets of a gelatin on said screens,and one or more high intensity ultra-violet lamps for irradiating andsterilizing said screens immediately prior to depositing the gelatinsheets thereon.

13. A process for the manufacture of dried gelatin material of lowbacterial content which comprises treating th drying support with ultraviolet radiation of sufficient high intensity and for a period of timesufficient to substantially sterilize the surface of the support and anygelatin adhering thereto and prior to any substantion recontaminationapplying the gelatin to said support for drying.

14. A process for the manufacture of dried gelatin material of lowbacterial content which comprises treating the drying support with ultraviolet radiation of suflicient high intensity and for a period of timesuificient to substantially sterilize the surface of the support and anygelatin adhering thereto and prior to any substantial recontaminationdrying a film of gelatin on said support.

15. In an apparatus for manufacturing gelatin, the combination of asource of ultra violet radiation, means for subjecting for apredetermined time a support for a gelatin film to rays from said sourceof radiation and means for depositing said gelatin film on said supportpromptly after the irradiation thereof.

16. In an apparatus for manufacturing gelatin, the combination of asource of ultra violet radiation, means for exposing for a predeterminedtime a support for a gelatin film in radiation relation with said ultraviolet and means for depositing said gelatin film on said supportimmediately after irradiation thereof.

WALTER M. URBAIN.

